Followup to PR espressif#126 (espressif#139)

* Followup to PR espressif#126

Forgot to mention the extra `pip install requests` in the ReadMe and saw issue espressif#134

* Update windows.md

Author: tobozo

doc/windows.md

@@ -11,7 +11,8 @@
 
     ```bash
     python -m pip install --upgrade pip && \
-    pip install pyserial
+    pip install pyserial && \
+    pip install requests
     ```
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